It can be solved when you switch Eidolon's position, such as I switch Hel to stand in front and Mordred stand back row, that way no Eidolon will die. But if I keep it like this Mordred always die before Perserus.

Kitwritten, I made and observation, normally I do full patern Green Orange Blue Green Orange Blue Green to get all 3 skill shots from mount, and when I do that after 6th attack from me I lose one.

But now I tried 3 times where I go Green Orange Blue Green Green Blue Green, I still get 3 skill shots but I dont lose a unit by skipping the fifth in pattern (the second time orange) tho I lose the effect of the 2 units I got who is fireunits :(